Flux for magnesium and alloys thereof



Patented Dec. 16, 1924.

UNITED STATES i PATENT OFFICE.

JOHN A. GANN, F MIDLAND. MICHIGAN, ASSIGNOR TO THE DOW CHEMICAL COM- PANY, OF MIDLAND, MICHIGAN, A CORPORATION OF MICHIGAN.

FLUX FOR MAGNESIUM AND ALLOYS THEREOF. A

No Drawing. Application filed July 9,

To all whom it mm/ concern:

Be it known that I, JOHN A. GANN, a

citizen of the United States, and a resident of Midland, county of Midland, and State of Michigan, have invented a new and useful Improvement in Fluxes for Magnesium and Alloys Thereof, of which the following is a specificatiomthe principle of the invention being herein explained and the best mode in which I have contemplated applying that principle, so as to distinguish it from other inventions.

Several different fluxes or mixtures of flux materials have heretofore been described and used either in connection with the elec--- the same time it must have theproper combination of specific gravity and surface tension in order not only to float the metal or alloy when in molten-condition but at the same time cover the same with a protecting film, in order to prevent undue oxidation thereof. Furthermore, there must of course be no chemical reaction between the flux and the metal. Very few salts or salt mixtures meet all of the foregoing re uirements, the majority being ruled out eit er because of too high melting point or because they react with the metal.

With the object accordingly of providing a flux that may be satisfactorily employed in the connection stated; I have discovered the combination of ingredients hereinafter fully described .and particularly pointed out in the claims, such ingredients being preferabl combined in the' manner similarly described and claimed. It will of course be understood that the following description sets forth but several of the various ingredi-.

enter as well as but several of the various 1923. Serial N0. 650,521.

one of the materials employed in the electrolytic production of the metal, serves also when in molten-condition as a flux or protective coating for the metal but has too high a melting point so that an alkali-metal chloride, e. g. sodium chloride, is ordinarily added to lower such melting point. The flux thus composed of magnesium chloride and sodium chloride is disclosed in U. S. Patent No. 1,377 ,37 4 and also in German Patent No. 122,312, the latter describing a flux consisting of equi-molecular weights of mag nesium chloride, sodium chloride and potassium chloride with the addition of a small amount of calcium fluoride.

' I have now discovered that calciumchld ride may be desirablyadded to the standard magnesium chloride-sodium chloride flux consisting, as aforesaid, of these two last mentioned ingredients in approximately equi molecular proportion, viz, approximately 60 per cent magnesium chloride and 40 per cent sodium chloride. A perfectly satisfactory flux is obtained by making a mixture of two-thirds of such standard flux and adding thereto one-third of the calcium chloride. As more. and more calcium chloride is added, the covering power of the resulting flux diminishes so that a flux containing per cent of such calcium chloride will not in general prove suitable. A specific composition that has been employed with excellent results consists of 42 per cent magnesium chloride, 28 per cent sodium chloride and 30 per cent calcium chloride.

The advantages of the foregoing flux are two-fold. First an additional lowering of the melting point is secured, making the flux more limpid, so that it separates more readily-from the alloy at the casting temperature used. For example, anhydrous magnesium chloride melts at about 1300 F., the above described magnesium chloride-sodium chloride flux at about 850 F., while my improved flux, where of the specific composition indicated above, melts at about 750 F. The second advantage presented by the present improved flux mixture is the decrease in cost. The preparation of anhydrous magnesium-chloride, as is well known, is difiicult and expensive, whereas ways in which the principle of the'invention \calcium chloride is very readily dehydrated ma be carried out.

nhydrou's magnesium chloride, which is without decomposition. Accordlifily by reducing the content of such y us .magnesium chloride and substituting the chloride-sodium chloride flux added to give the desired composition. Another way is to add the sodium chloride to the calcium chloride and then heat the mixture until such calcium chloride is dehydrated, whereupon anhydrous magnesium chloride is added. Still another way is to melt and dehydrate a mixture of calcium chloride and sodium chloride, as last described above, and

then slowly feed in the hydrated magnesium chloride-ammonium chloride double salt and continue heating until the mixture is dehydrated and free from ammonium chloride. F

It should be stated in conclusion that wherever I have specified sodium chloride in 'describing 'my improved flux, potassium chloride may be substituted, i. e. both such alkali metal chlorides are, so far as I. am at present aware, equally satisfactory for the purpose.

Other forms-may be employed embodying the features of my invention instead of the one here explained, change being made in A the form or construction, provided the in-' gredients' stated by any of the following claims or the equivalent of suchstated ingredients be employed.

, I therefore" particularly tinctly claim as my invention f 1. A flux for use with molten magnesium point out and disand alloys thereof, wherein magnesium largely predominates, such flux consisting of a mixture of magnesium chloride, an alkali metal chloride and calcium chloride.-

2. A flux for use with molten magnesium and alloys thereof, wherein magnesium largely predominates, such flux consisting of a mixture of magnesium chloride and an alkali metal chloride with a relatively smaller amount of 'alcium chloride added.

.3. A flux for use with molten magnesium and alloys thereof, wherein magnesium largely predominates, such flux consistin of a mixture of magnesium and sodium 0 lo rides with a relatively sinaller amount of calcium chloride added.

' 4. A flux for use with molten magnesium and alloys thereof, wherein 1 magnesium largelypredominates,such flux consistin of a mixture of magnesium and sodium e lorides in aproximately' equimolecular proportions with a relatively smaller'amount of calcium chloride added.

5. A flux for use with molten magnesium and alloys thereof wherein .magnesium largely predominates, such flux consisting approximately of two-thirds of a mixture of magnesiuniand sodium chlorides in approximately equimolecular proportions and one-third of calcium chloride.

- 6. A flux for use with molten magnesium and alloys thereof wherein magnesium largely predominates, such flux consisting. approximately of forty-two (42) per cent of magnesium chloride, twenty-eight (28) per 7 cent of sodium chloride, and th rty (30) per cent of calcium chloride. Signed by me, this 5th day of JOHN A. GANN.

Jul 1923. g I 

